In Liu Cixin's short science fiction novel "The Village Teacher," Earth, a planet where a level 3C civilization exists, is at the top of the first spiral arm and the most inhospitable region of the galaxy.
Although this is a fictional setting and plot, according to current human knowledge, Earth is only a "drop in the ocean" in a tiny galaxy. Therefore, the search for the existence of alien civilizations in the galaxy has become the goal of scientists.
▲ Image from: NASA
Not long ago, in a new paper published in an arXiv preprint by Alberto Caballero of the University of Vigo in Spain, there was a bold prediction that four 'malevolent alien civilizations' may well be lurking in this galaxy we live in. And that some of these civilizations may be technologically similar to humans, but not yet capable of interstellar travel.
In late 2020, Alberto Caballero also submitted a paper in the arXiv preprint on the origin of the "WOW!" signal, which was detected in 1977 by the Big Ear radio telescope at Ohio State University and appears to have come from the direction of Sagittarius.
▲Image from: OSURO
Alberto Caballero mentioned that the "WOW!" signal is considered to be the best SETI radio signal candidate that we have found with telescopes (SETI is the collective name for all groups searching for extraterrestrial civilizations that use advanced equipment such as radio telescopes to receive and analyze electromagnetic waves coming from the universe in the hope of discovering extraterrestrial civilizations).
▲ Image from: OSURO
And in Alberto Caballero's paper not long ago speculating about a 'malevolent alien civilization' in the galaxy, there is actually no concrete basis in space to corroborate this idea, but rather by extrapolation.
In this paper, Alberto Caballero's extrapolation goes like this, using the probability of a human civilization attacking or invading an inhabited exoplanet if it reached a Type I civilization that could travel interstellar nearby in the Kardashev class to estimate the invasion probability of a 'malicious alien civilization'.
▲Image from: arXiv
The Kardashev scale mentioned here is a method used to measure the advanced level of a civilization's technology, based on how much energy a civilization can use to communicate with the outer planets. The type I of this indicates that the civilization is the master of the planet's energy, meaning that it can dominate the sum of the energy of this planet as well as the surrounding moons.
In order to make inferences, Alberto Caballero compiled a list of countries that had invaded other countries between 1915 and 2022 and found that a total of 51 countries had initiated some type of invasion during this period.
▲Image from: arXiv
After calculating the weighted probability of invasion for each country (each country's probability of invasion is weighted by its percentage of global military spending), and considering that there are 195 official countries on Earth, and considering that a malevolent civilization would indeed pose a threat, Alberto Caballero concludes that the probability of an alien civilization invading Earth is about 0.028%.
In addition, the article mentions that humans are expected to be a Type I civilization capable of interstellar travel in about 259 years, and the estimated probability of an Earth civilization invading another civilization at that time is 0.0014%.
▲Image from: BenQ
These inferences cannot actually be confirmed at this time, though Alberto Caballero also says that the likelihood of a malevolent civilization invading Earth is extremely low, probably similar to the likelihood of an asteroid collision causing a global catastrophe.
Interestingly, he also mentions the reason SETI has not made any serious attempt to send radio messages to potentially habitable exoplanets.
▲ Image from: Unsplash
The reason why there is no international debate on the possibility of doing so is that there is a general fear in the scientific community that the information sent could be accessed by an extraterrestrial civilization with malicious intent. Such a civilization might be more advanced than ours and might be interested in exploiting the resources of our planet by force.
Human beings who have always aspired to go out of the Earth and longed to see the universe are too 'fragile' at the moment, but even so, although they may fear that they will meet with disadvantages, they will not stop exploring space. Perhaps in the future, mankind will really be able to achieve interstellar travel and go beyond the 'Blue Star' to deep space.